Recently, as symbolized by the 1992 Earth Environmental Summit, worldwide attention has been focused on the earth's environmental problems, and how to protect the earth's environment has become a worldwide problem for industrial technology.
For example, approximately 30% of the world's land area is currently occupied by deserts, and this area continues to increase. While there are various causes for this, many of them are environmentally destructive factors associated with the production activity of human beings, such as overlogging of trees, environmental pollution including acid rain, massive pumping of underground water, and abnormal weather conditions which are believed to be caused by the destruction of the ozone layer and an increase in the production of carbon dioxide gas. At the same time, the world population continues to increase every year.
In order to prevent food shortages associated with this population growth, it is necessary to revive the soil which is dead as a result of desertification, as well as to prevent future desertification of the soil.
Conventionally, methods have been carried out which increase the water content of the soil by building canals for irrigation and artificially precipitating rain. However, these methods are not a fundamental improvement in the soil structure, and the supplied water soon seeps out, resulting in a poor efficiency of water use. Therefore, in order to efficiently prevent desertification, it is necessary to improve the soil structure itself.
For the purpose of avoiding food shortages, there have been efforts to improve the crops themselves using biotechnology techniques to increase productivity. Yet in order to increase the productivity of crops, it is necessary to improve the soil in which crops grow such that the soil is suitable for each crop. However, although soil improvements such as plowing the soil surface or adding fertilizers have been routinely carried out, there have not been attempts to artificially build layers in the soil for the purpose of fundamentally improving the soil environment based on the soil structure, i.e. fundamentally improving the structure of the soil itself.
Furthermore, in modern societies, partly because of population growth, numerous structures have been built, by various public engineering works, building construction, etc. For these structures, needless to say, the foundation ground plays a very important role, and to maintain a stable foundation ground for many years it is necessary to fundamentally improve the environmental characteristics of the soil at the ground level so that they are suitable for the structures.
As described above, the improvement of soil structure is becoming necessary in order to make the environmental characteristics of the soil desirable for human beings in a total planetary environment. The environmental characteristics of soil are often determined by the water content of the soil. Therefore, it is of primary importance to improve the soil structure in such a way that the water content of the soil can be artificially controlled.
Conventionally, means to control the water content of soil have been proposed, for example, a mixture of soil and a water-retentive polymer compounds(s), and surface treatment of the soil with polymer hydrogen siloxane as described in the Japanese unexamined patent publication (Tokkai) Hei 1-319585.
Although the methods described above are expected to have an effect as means of controlling the water content in soil, it must be said that their effect still falls short of preventing land desertification, and more effective methods have been sought.